Low pressure flotation cell



June 27, 1933.. w SHEELER 1,916,020

LOW PRESSURE FLOTATION CELL Filed Jan. 23, 1930 INVENTOR WA LTER LE ON SHEELER ATTORNEYS Patented June 27, 1933 UNITED STATES PATENT? OFFICE LOW PRESSURE FLOTATIO'N CELL Application filed January 23, 1930.

This invention is addressed to a novel cell structure of ore flotation.

One of the objects of the invention is to afford a large capacity, with a relatively low 5 level of the solution, and it is a feature of the invention to obtain prolonged duration contact of the ore values with the frothing agent and the re-agents so as effectively to clean and film or coat the ore values and facilitate collection of the latter by the bubbles in a plurality of stream paths of travel that are relatively short in length.

It is a prime desideratum of the invention to perform the function of intermin- 5 gling the air or gas with the solution and rendering the latter buoyantly ascendent through the various paths of travel, with a low or minimum of pressure of such gaseous agent so as to effect the greatest possible economy of power.

It is a further feature of the invention to employ a current accelerater device for each ascending bubble stream and in the most improved form of the invention, these devices not only function to accelerate said streams but also to break up and destroy any large bubbles that might possibly form therein and thereby cause the formation of smaller bubbles and a consequent and thorough diffusion of the gaseous agent and reagent throughout such streams while the latter are ascending.

In the preferred form of the invention, the

accelerating devices are in the form of vena contract-a or venturi, one for each of the series of bubble streams, and said Venturi pipes, or stream forming pipes, function to accelerate flow movement therethrough for a portion of the length of said pipes, and

thereafter, to reduce the stream velocity and expand the streams, whereby a differential of flow is caused such as to function most effectively in advancing diffusion of the gaseous agent and also to expose the expanded and retarded streams to atmosphere and cause an intensive frothing.

It is a further feature of the invention, after the several bubble streams have been thoroughly permeated with the gaseouS Serial No. 422,880.

agent, to permit them to ascendently accumulate and build up in an expansion chamber that is common to all of said streams, in which chamber the gas permeated and frothed solution is exposed to atmosphere, 55 preferably above the solution level, and onto which latter the f othed solution is free to discharge by gravity.

It is a feature of the invention slightly to limit the extent of expansion of the froth so in the expansion chamber as compared to that to which the froth is capable, and which expansion is considered preliminary or an initial aeration, with a view of causing the froth to build up cumulatively to various heights, so that it can cascade down onto the solution level over louvres.

It is also a feature of the invention to afford the frothed pulp that discharges from the expansion chamber or which cascades over the louvres down onto the pulp level, a free and unrestrained movement outwardly toward and into the launders along the substantially quiescent pulp level, such free and unrestrained movement consisting in not forcing or causing a submergence of the discharged froth under the pulp level, during movement of such froth from the expansion chamber or cascading louvres and until the froth actually enters the launders. 80

Fig. 1 is a sectional view of the cell taken on the line 11 of Figure 2. v

Fig. 2 is a sectional view taken on the line 22 of Figure 1.

In the drawing like characters of reference indicate corresponding parts in each figure.

The numeral 1 indicates generally a chame ber having a bottom Wall :2, side walls 8, end walls 4 and 5 and converging walls 6. The side walls 3 are of lesser height than the end 'walls at and 5 to form weirs over which the froth from the cell may flow to longitudinally arranged launders 7 having suitable outlets, not shown. The end walls i is provided with a central bottom opening 8 communicating with a feed hopper 9 and the end wall 5 is also provided with a central bottom opening 10 communicating with a discharge chamber 11 fitted with a weir 12 and a suitable outlet pipe 13. The sides of the discharge chamber 11 above the weir 12 are provided with fillets 1 1 which are adapted to support one or more narrow boards 15 which serve to reduce the vertical height of the opening as required to adjust the overflow level of the tank 1.

Extending between the end walls t and is an inverted channel 16 which is spaced from the bottom wall 2 and is wider at its face than its upper extremity and above this channel is an upper channel 17 formed with upwardly diverging sides 18 which are surmounted with walls 19 and louvres 20, the louvres on opposite sides being arranged downwardly diverging.

Communicating between the channels 16 and 17 is a plurality of fittings 21 each in the form of a vena contracta, the purpose of which will hereinafter appear. Extending downwardly above each series of louvres and substantially parallel thereto are fixed baffies 22 each of which is provided at its lower edge with a hinged battle extension which latter is provided with rod 21- or other suitable device by which the battle extension may be set at any desired angle to control the outward flow of froth discharged through the louvres 20. Vertical. walls 25 extend from the-upper end of each of the baffles 22 and are fitted on their inner sides with staggered downwardly inclined bafiles 26 to form a chamber 27 through which any excess of air may freely flow. I

Extending longitudinally of the tank 1 is one or more pairs of pipes 28 which are fitted with valves 29 and downwardly converging branches 30. The branch pipes 30 are arranged in pairs and converge towards each other, each pair being adapted to discharge a. flow of air or gas below the verticalaxis of a vena contracta 21. The bottom wall 2 of the tank 1 is fitted with a suitable numher of discharge pipes 31 for the purpose of removing the residue from the base of the tank after operation.

Having thus describe( the several parts of my invention I will now briefly explain its operation.

Treated ore is delivered into the feed hopoer 9 in a continuous stream and air or gas is admitted at suitable pressure to the pipes 28 and through the valves 29, which are adjusted to pass the-air or gas in the desired quantity through the branch pipes 30. The -oulp level is maintained at any suitable height by adjusting the height of the weir 12, but present practice shows an effective level to be within the length of the fittings which is considerably below the level of the owermost gap between the batlles 20 and below the battles 22 or their extensions 23, thus permitting the froth to flow freely and obviating the necessity of forcing it downwards into the body of the pulp, thereby reducing the static head to be overcome by the entering air and enabling the cell to be effectively operated at an air pressure of eleven ounces or less. The air from each pair of opposed pipes is forced by its eleven ounce or other pressure in two downwardly opposed streams, the downward tendency of which is overcome to a large extent by the upward pressure of pulp immediately below. The air streams therefore, being directed towards each other produce an air discharge in the form of a fan, the plane of which is vertical and extends longitudinally of the cell. This fan formation of air is obviously extremely thin and in consequence breaks up into a relatively narrow line of extremely small bubbles all tending to rise at a rapid rate through the fittings 21 producing an appreciable suction inwardly from the converging side walls 6 of the cell. The suction thus produced is such that oil or chemical which will normally float on the pulp surface of a cell innnediatelydisturbed and mixed into the pulp as it flows towards the mouth of the inverted channel 16.

The turbulence caused by suction incidental to the discharge of a r in a transversely confined stream keeps the metallic mineral particles in moti n so that they are effectively attacked by the air bubble stream to render them buoyant when they are rapidly projected through the lower or converging half of the fittings 21. Since the air stream is extremely thin no large bubbles can be formed and in consequence no air is inetl'ectively employed and the quantity of metallic mineral raised is proportionately high. As soon as the bubbles pass into the upper half of the fittings their velocity is reduced so that no back pressure is developed against the air flow emanating from the jets so that the froth is slowly carried up through the upper channel 17 and passes freely out through the louvres 20 and slowly spreads outwards under the betlles 22 affording ample time for the gangue to detach itself from the froth and sink to the base of the cell from whence it is finally discharged over the weir 12 while the metallic. mineral bearing froth is discharged into the launders 7.

It will be obvious that by providing the cell with a plurality of upcast passages through the fittings 21 and supplying separate air flow to each passage. that the quantity of air flow may be so adjusted as to give a greater agitation to the pulp adjacent one end than the other, thus ensuring the complete separation of the metallic mineral from the ganguc.

it will also be apparent that any desired variety of gases may be introduced through different branch pipes to float different values as they flow through the cell. which values could be separated within reasonable limits by fitting; battles transversely of the tank 1 and the channel 17 and dividing the launders into corresponding units, thus virtually making the tank into a multiple unit cell having acommon pulp delivery and discharge for each of the divisions.

In further emphasis of certain phases of the operation, it will be noted that the series of pipes 21, irrespectively of whether the same are of the Venturi type, serveto form a series of bubble streams which. with the solution in the tank, take endless paths, which latter of course are not prescribed. How ever, it will now be clear that portions of the solution may be treated many times in each pipe 21 or in all of them, and consequently, the pipes 21 act supplementally and a plurality of times on the solution as the latter travels through the tank. This fact, together with the fact that instead of a single body upflow of the solution, I obtain simultaneous movement thereof at a rapid rate, through a plurality of independently acting diffusion pipes 21; not only enables me to operate with a low gas pressure, but at a low level in the tank. Hence, I obtain prolonged duration contact of the values with the reagent and frothing agent, which is necessary to obtain a maximum recovery of the values.

lVhile in the particular structure shown, the nozzle ends of branch pipes 30 terminate in opposed and alined relation to discharge the gas in a fan or blade-like form, as described, and while this novel format-ion is or would be advantageous in obtaining an attenuated stream of gas that would retard if not prevent altogether, the formation of large bubbles before the stream meets the restriction, still, attenuation of discharge, even in the form shown, does not alter the fact that a relatively large volume of gas is delivered to each venturi 21. This is amply evidenced by the fact that I have shown four pipes 30, delivering to each venturi 21, affording each thereof, a large volume of gas, under low pressure, for the purpose of rendering the bubble streams very ascendently buoyant, and it is because of this large volume of gas entering each venturi, that I obtain such a rapid movement into the venturi, together with the restriction of the latter, that the turbulence of current is so effective. Therefore, it should now be clear, that while I celiver the gas in an attenuated stream or streams, to the venturi, and under low'pressure, I obtain a relatively very large volume of gas discharge. The above will also explain. why I can operate at such a low solution level.

As the is admitted, to initiate and sustain the bubble forming streams through the venturi by venturi action, the latter serve to accelerate stream velocity until the restriction is reached, whereupon the stream velocity decreases as expansion takes place, and hence, the upper portion of each venturi forms an independent expansion ch anioer, subject to atmosphere. As the velocity decreases, there results a difierential of flow, that further advances and perfects diffusion of the gases in each stream, even before the latter reach the expansion chamber 17, which is fully exposed to atmosphere.

Now it will be clear, that if any large bubbles form before the stream reaches the restriction in the venturi, the latter, in addition to its accelerating function, will, by circumferentially restricting the stream, also break up such large bubbles, causing diffusion of the gas, and effecting thereby reformation of the large bubbles into a multitude of small bubbles approximating froth.

It may be explained, that if the expansion chamber 17, common to all the venturi 21, were of a size to afford the fullest possible expansion of the froth, the latter would not build up in the desired manner, hence, the expansion chamber 17, is relatively limited in size to cause the froth cumulatively to build up therein, and as the froth attains an elevation equal to the height of any of the spaces between the louvres, it is free to cascade down over the latter onto the froth on the pulp level in the tank for the fullest aeration and frothing, which is a valuable feature.

It should now be clear that I do not cascade primarily to cause frothing, or to obtain requisite aeration, as both are operatively effectively attained in the expansion chamber, and in the absence of cascading, the froth could, under some conditions discharge directly from the expansion chamber 17, onto the solution level, without any appreciable drop. However, the cascading I obtain, although not from a high point or elevation, is advantageous and beneficial in promoting the fullest development of both frothing and aeration.

The level of the pulp solution, indicated at A, which is an effective level although not a necessary level, shows that the cell is a shallow depth cell and that the upper ends of the venturi 21 extend above the pulp level, and could in the abscence of the walls 17, of the expansion chamber, deliver frothed solution down onto the pulp level to thereby increase aeration. However, in a broader sense, and from; the standpoint of patentability, the walls 17 may rightly be considered an upward extension of the venturi and where it is possible to operate without the louvres 20, as it many times is, the frothed solution could cascade down onto the pulp solution level from over the tops of the upper ends of the Venturi pipe devices, which, as will be seen, are open to atmosphere.

What I claim as my invention is:

1. A flotation cell comprising a tank through which treated pulp is adapted to flow from a feed hopper to a discharge chamher, an inverted substantially V'shaped channel extending along the tank in the direction of the pulp flow, a further V-shaped channel thereabove having louvred side walls and a plurality of tubular fittings communicating between the channels, and means for delivering gas under each of said fittings to agitate the pulp and circulate it upwards through the fittings and the louvres.

2. A flotation cell comprising a tank through which treated pulp is adapted to flow from a feed hopper to a discharge chamber, an inverted substantially V-shaped channel extending along the tank in the direction of the pulp flow, a further V-shaped channel thereabove having louvred side walls and a plurality of tubular fittings communicating between the channels, and means for delivering gas under each of said fittings to agitate the pulp and circulate it upwards through the fittings and the louvres, and means for selectively cont-rolling the admission of gas to each of the fittings.

3. A flotation cell comprising a tank throughwhieh treated pulp is adapted to flow from a feed hopper to a discharge chamher, an inverted substantially V-shaped channel extending along the tank in the direction of the pulp flow, a further V-shaped channel thereabove having louvred side walls, a constricted passage communicating between the channels, means for delivering gas under the lower channel to agitate the pulp and circulate it upwards through the constricted passage, a pair of baflies exterior of the louvred side walls, and means for varying the incli nation of the baflles.

4. A shallow depth and low pressure mineral flotation mechanism, comprising, a tank for the pulp solution, a plurality of independently acting" Venturi pipes vertically disposed in said tank on a horizontal plane and having their lower ingress ends immersed in and open to the solution, a horizontally disposed expansion chamber above the solution and to which all or" the upper ends of said pipes deliver, and means for each pipe delivering a gaseous agent thereto at low pressure and large volume to render the solution in said pipes buoyantly ascendent and form in each pipe a mineral collecting bubble stream, and said expansion chamber being located in a position to discharge'overflow froth onto the surface of the pulp body.

5. A shallow depth and low pressure mineral flotation mechanism, comprising, a tank for the pulp solution, an expansion troughlike chamber exposed to atmosphere and located to overflow onto the pulp level as the froth cumulatively builds up in said chamber, a horizontally disposed series of inclependently acting stream forming vertical pipes having lower ingress ends immersed in the solution and opening thereto and upper egress ends delivering to said expansion chamber, thereby forming with the solution a series of endless solution paths in said tank whereby portions of the solution may pass a plurality of times through any one or all of said pipes, and each pipe having a gaseous feed device delivering thereto a gaseous agent to form in each pipe a mineral collecting bubble stream.

6. A shallow depth and low pressure mineral flotation mechanism, comprising, a tank for the pulp solution, a limited expansion chamber exposed to atmosphere in which froth may cumulatively build up, a series of spaced louvres extending upwardly from and communicating with said chamber and over which louvres the cumulated froth may cascade down onto the pulp level, a horizontally disposed series of vertical Venturi pipes immersed in the solution and having lower ingress ends opening to the solution and upper egress ends delivering to said expansion chamber thereby forming with the solution a series of endless path of solution travel whereby portions of the solution may be supplementally treated in each or all of said pipes to prolong contact of the solid values with the re-agent and frothing agent, each Venturi pipe having a plurality of gas pipes delivering a gaseous agent to 1ts ingress end at low pressure and large volume to buoyantly initiate and sustain an ascending mineral collecting bubble stream therein, and each gas pipe having a valve whereby gas delivery to said Venturi pipes may be altered to vary the action on the solution passing therethrough with respect to the action on the solution in the remaining Venturi pipes.

7. A shallow depth low pressure flotation cell, comprising, a tank for the pulp solution, a plurality of Venturi pipe devices substantially vertically disposed in said tank and having lower open ends immersed in and in unrestrained communication with all of the solution in said tank whereby any portion of the solution may be treated a plurality of times in any one or all of said pipe devices, the upper ends of said pipe devices being above the solution level in said tank and adapted to cascade frothed solution down onto the solution level and said upper ends being open to atmosphere, and each Venturi pipe device having a gaseous feed means delivering thereto a gaseous agent under low pressure and in suflicient volume to buoyantly initiate and sustain an ascending mineral collecting bubble stream therein by Venturi action.

8. A low pressure shallow depth flotation cell, comprising, a tank for the pulp solution, a plurality of mineral collecting bubble stream forming pipes having lower ends immersed in said solution, means for causing the solution to ascend in said pipes, and an expansion chamber to which the upper ends of said pipes deliver and said chamber being open to atmosphere and being disposed above the solution level and adapted to cascade the frothed solution delivered thereto by said pipes down onto the solution level.

9. A low pressure shallow depth flotation cell, comprising, a tank for the pulp solution, a plurality of substantially vertically disposed mineral collecting bubble stream forming pipes having their lower ends i1nmersed in said solution, means for causing a gaseous agent to efliect ascension of said streams in said pipes, an expansion chamber to which the upper ends of said pipes deliver and said chamber being open to atmosphere and being disposed above and adapted to cascade the frothed solution down onto the solution level, and sets of louvres spaced above said chamber and over which the frothed solution is adapted to cascade down onto the solution from various heights as the froth accumulates in said expansion chamber.

10. A low pressure mineral flotation mechanism comprising a tank for the pulp solution, a plurality of independent open Venturi pipes located with their axes vertical in said tank and extending from below to above the liquid level therein, means for feeding gas under low pressure into the lower end of each Venturi pipe whereby to initiate and sustain a free and direct upward movement of mixed pulp solution and gas in said pipes so that the discharge from said pipes will occur above the liquid level for permitting free expansion of said gas and thus a free frothing of the mixture, and walls for forming an expansion chamber above the pipes and adapted to limit the movement of froth while permitting return of liquid to the lower ends of said pipes.

11. A flotation cell comprising a tank for the pulp solution, a Venturi pipe located with its vertical in said tank, at least one pair of gas supply pipes opening into said tank beneath the venturi for delivering gas into the solution, the mouths of said pairs of supply pipes being opposite one another so that the gas streams therefrom may encounter one another and produce a fan-like film of gas beneath the Venturi pipe, and individual means for regulating the flow of gas in each said supply pipe.

12. A flotation cell as in claim 11, in which the mouths of said pairs of pipes are spaced on opposite sides of a vertical plane through the Venturi axis whereby the fan-like film may be formed in said plane.

13. A flotation cell comprising a tank for the pulp solution, a Venturi pipe located with its axis vertical in said tank, a plurality of pairs of gas supply pipes opening into said tank beneath said Venturi pipe for delivering gas into the solution, the mouths of said pairs of supply pipes being opposite one another so that the gas streams therefrom may encounter one another and produce a fan-like film of gas beneath the Venturi pipe, and individual means for regulating the flow of gas in each supply pipe.

let. A low pressure mineral flotation apparatus comprising a tank for the pulp solution, a plurality of independent means operating under a pressure not exceeding eleven ounces for supplying gas in an ascending stream of bubbles into the solution in said tank, and Venturi conduit devices located in the path of the ascending stream of bubbles and affording direct vertical upward passage therethrough for mixed solution and gas, said devices each having large open horizontal cross-sections at top and bottom and a lesser horizontal cross-section intermediate its length and affording direct and free vertical passage for the mixed gas and pulp solution and extending from below to above the normal liquid level in said tank so that a circulation of the solution is-produced by the gas-lift effect and the mixed solution and gas is'discharged above the solution remaining in the tank, and means for providing a common expansion chamber above said conduit devices, said chamber being of greater horizontal cross-section than all of said devices and permitting the return of liquid to the bottoms of said devices.

15. A mineral flotation apparatus comprising a tank for the pulp solution, means for supplying gas under low pressure into said tank beneath the liquid level therein, a plurality of independent vertical conduit means each having large open horizontal cross sections at top and bottom and a lesser horizontal cross section intermediate its length and affording direct and free vertical passag-e for the mixed gas and pulp solution, 1

means open to all said conduit means for providing a common expansion chamber above said conduit means for permitting the separation of froth from liquid, said expansion chamber being open at its bottom to said tank for the return of solution thereto, and adjustable baifles for forming the upper walls of the opening between said chamber and tank whereby to control the outward move ment of froth in said chamber.

Dated at Silverton this 24 day of December,1929.

WALTER LEON SHEELER. 

